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High Level Trigger b-tagging
INTRODUCTION
Tagging b-jets at the trigger level can expand the physics reach of ATLAS in many ways: it allows to lower the jet ET threshold to increase the acceptance of interesting physics events containing multiple b-jets (like bbH and ttH ), and can be used to reduce non-b backgrounds and improve the purity of Super-symmetry searches involving b-jets in the ?nal state.
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Current and future work involves the optimization of the operational parameters of the algorithm, determination of performance in real data events, on-line and off-line validation, and the investigation of new trigger menus involving b-quarks and missing transverse energy for Super-symmetry searches.
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The IPChi2 tagger is based on the impact parameter distribution of mis-tags, which can be derived directly from data and does not require the use of Monte Carlo templates as in the likelihood ratio b-tagger.
b+MET combined trigger
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